MX341 AVR Exact Generic Replacement MX341 is a phase detection automatic voltage regulator and is part of the excitation system of a brushless generator. The excitation power is derived from a three-phase permanent magnet generator (PMG), to isolate the control circuits of the AVR from the effects of non-linear loads and to reduce radio frequency interference on the terminals of the generator. The extended short-circuit current of the generator is another feature of the PMG system.